The general responses of microorganisms to environmental onslaughts are modulated by altering the gene expression pattern to reduce damage in the cell and produce compensating stress responses. The present study attempts to unravel the response of the Gram-positive Exiguobacterium sp. PS NCIM 5463 in the presence of [As(III)] and arsenate [As(V)] using comparative proteomics via two-dimension gel electrophoresis (2-DE) coupled with identification of proteins using matrix-assisted laser desorption/ionisation (MALDI-TOF/MALDI-TOF/TOF). Out of 926 Coomassie-stained proteins, 45 were differentially expressed (p < 0.05). Considering the resolution and abundance level, 24 spots (peptides) were subjected to MALDI analysis, identified and categorised into several functional categories, viz., nitrogen metabolism, energy and stress regulators, carbohydrate metabolism, protein synthesis components and others. A functional role of each protein is discussed in Exiguobacterium sp. PS 5463 under arsenic stress and validated at their transcript level using a quantitative real-time polymerase chain reaction. Unlike previous reports that unravel the responses toward arsenic stress in Gram-negative organisms, the present study identified new proteins under arsenic stress in a Gram-positive organism, Exiguobacterium sp. PS NCIM 5463, which could elucidate the physiology of organisms under arsenic stress.

Summary: Nanomaterials are getting a great deal of attention because of their potential to achieve specific processes and selectivity, especially in biological and pharmaceutical applications including generation of bioactive compounds. TiO 2 nanoparticles because of their chemical stability, biological inertness and high stability are largely used in various fields. Thus, their toxicity evaluation becomes must. In the present study, TiO 2 nanoparticles were synthesized and characterized using TEM and XRD. Average particle size was estimated to be $18 AE 2 nm. Particles are agglomerated and mostly in spherical shape. TiO 2 nanoparticles were found to show inhibitory effect on the growth of E. coli bacterial strain in a dose dependent manner.

Objective: To study the effect of the mutation in conserved G412E in Cct7p subunit of CCT complex on its cellular fate. Results: TriC/CCT is a dynamic multimeric protein that assists in protein folding in energy-dependent manner. A point mutation in the ATP binding pocket in the equatorial domain of Cct7p subunit causes a delay in doubling time. The cell’s size was twice the wild type, and the formation of protein aggregates suggests disturbed folding of the proteins. Upon growing in stressful conditions of arsenous acid and cadmium chloride, mutant was found to be lethal in As3+ but grew well in Cd2+ with 10.59µg cadmium uptake mg− 1 compared to wild type. The increased expression of vacuole transporters YCF1 and BPT1 by ten-fold and two-fold in mutant indicates the metal transportation to the vacuole. Conclusion: CCT complex was vulnerable to the mutation in G412E in Cct7p subunit of protein folding molecular machinery. Interestingly, already stressed cells provided robustness against oxidative stress and cadmium sequestration in the vacuole.

To study the effect of the mutation in conserved G412E in Cct7p subunit of CCT complex on its cellular fate. Results:TriC/CCT is a dynamic multimeric protein that assists in protein folding in energy-dependent manner. A point mutation in the ATP binding pocket in the equatorial domain of Cct7p subunit causes a delay in doubling time. The cell's size was twice the wild type, and the formation of protein aggregates suggests disturbed folding of the proteins. Upon growing in stressful conditions of arsenous acid and cadmium chloride, mutant was found to be lethal in As 3+ but grew well in Cd 2+ with 10.59µg cadmium uptake mg − 1 compared to wild type. The increased expression of vacuole transporters YCF1 and BPT1 by ten-fold and two-fold in mutant indicates the metal transportation to the vacuole. Conclusion:CCT complex was vulnerable to the mutation in G412E in Cct7p subunit of protein folding molecular machinery. Interestingly, already stressed cells provided robustness against oxidative stress and cadmium sequestration in the vacuole.

Objective: To inspect the role CCT in cell wall maintenance. Results: The chaperonin TRiC/CCT is cytosolic cylindrical complex of 16 subunits encoded by eight essential genes CCT1-8. It contributes to folding 10% of cellular polypeptides in yeast. The strain carrying substitution point mutation G412E in the equatorial domain of Cct7p resulted in the improper folding of substrates. In this study, the CCT7 mutant exhibited sensitivity to non-optimal growth temperatures and cell wall stressors. Heat shock is known to disrupt cell wall and protein stability in budding yeast. Mitogen-activated protein kinase-mediated cell wall integrity pathway gets activated to compensate the perturbed cell wall. Overexpression of the PKC1 and SLT2 genes of MAPK signaling pathway in mutant rescued the growth and cell division defects. Additionally, the genes of the CWI pathway such as SED1, GFA1, PIR1, and RIM21 are down-regulated. Conclusions: The Cct7p mutant strain (G412E) is unable to withstand the heat stress due to the underlying defects in protein folding and cell wall maintenance. Taken together, our results strongly indicate the interaction between CCT and cell wall integrity pathway.